1. Field of the Invention
The present invention relates to a head chip, a liquid jet head, a liquid jet recording device, and a method of manufacturing the head chip.
2. Description of the Related Art
In recent years, there have been provided a large number of liquid jet type recording devices that eject an ink droplet on a recording medium such as a recording paper for recording an image or a character thereon. For example, a printer or a facsimile is an example thereof. The recording device supplies ink to a head chip from an ink tank through an ink supply pipe, and ejects ink onto the recording medium from a nozzle of the head chip for recording.
FIG. 9 is a plan view of a head chip according to a related art, and FIG. 10 is a cross-sectional view taken along the line E-E of FIG. 9. As illustrated in FIG. 10, a head chip 41 includes an actuator plate 15 with a plurality of channels 12, a nozzle plate 14 with nozzles 13 that communicate with the channels 12, and a cover plate 16 that covers the channels 12.
FIG. 5 is a cross-sectional view of a part taken along the line F-F of FIG. 9. As illustrated in FIG. 5, liquid jet channels (hereinafter referred to simply as “jet channels”) 12A that eject ink, and dummy channels 12B that eject no ink are alternately formed in the actuator plate 15. The entire actuator plate 15 is made of a piezoelectric material, and thus the jet channel 12A is held between a pair of piezoelectric elements 11. Each of the piezoelectric elements 11 includes a common electrode 18a on the jet channel 12A side, and a drive electrode 18b on the dummy channel 12B side. The common electrodes 18a are grounded, and the same voltage is applied to the drive electrodes 18b of the pair of piezoelectric elements 11 that hold each jet channel 12A. As a result, a pressure fluctuation is generated in the ink that is filled inside the jet channel 12A, and an ink droplet is ejected from each nozzle 13.
As illustrated in FIG. 10, a common terminal 19a connected to the common electrode 18a is formed on a surface of the actuator plate 15. As illustrated in FIG. 9, a drive terminal 19b connected to each drive electrode is also formed on the surface of the actuator plate 15. The common electrodes 19a and the drive terminals 19b are connected externally, and thus a flexible substrate 90 is mounted on a surface end of the actuator plate 15 through an anisotropic conductive film (not shown) or the like. That is, wirings 92a and 92b of the flexible substrate 90 are connected to the common terminals 19a and the drive terminals 19b of the actuator plate 15, respectively. As illustrated in FIG. 10, in order to prevent the common terminals 19a and the drive terminals 19b from being short-circuited by the wirings 92 of the flexible substrate 90, a coverlay 98 made of an insulating material is formed on the surfaces of the wirings 92.
As illustrated in FIG. 9, common terminals 19a and drive terminals 19b are arranged at narrow pitches. For that reason, there is a risk that those terminals may be short-circuited when the flexible substrate 90 is mounted. In particular, in recent years, in order to record highly fine images and characters on a recording medium, the pitches of the jet channels of the head chip 41 are required to be narrow. Along with the narrowed pitches of the jet channels, the pitches of the respective terminals 19a and 19b are further narrowed. Therefore, the above-mentioned problem becomes more remarkable.
Further, the respective terminals 19a and 19b of the actuator plate 15 and the wirings 92 of the flexible substrate 90 are small in line width because those elements are arranged at narrow pitches. On the other hand, the actuator plate 15 is made of a ceramic-based piezoelectric material whereas the flexible substrate 90 is made of a resin material such as polyimide. For that reason, those members are largely different in linear thermal expansion coefficient from each other, and a difference in the amount of expansion and contraction between those members due to a temperature change becomes large. As a result, it is difficult to align the respective terminals of the actuator plate 15 with the wirings of the flexible substrate 90.
JP 09-29977 A discloses a configuration in which, in order to facilitate the connection of electric wirings even if the groove intervals of an ink chamber are narrowed, electrode extraction parts that are rendered conductive to an electrode disposed within the ink chamber is formed on the surface of a piezoelectric ceramic substrate, and the intervals of the electrode extraction parts are radially formed so as to be larger than the intervals of the electrodes. However, the technology of JP 09-29977 A has such a problem that the intervals of the electrode extraction parts are widened, and hence the piezoelectric ceramics substrate large in width is required, resulting in the upsized ink jet head.